Pharmacokinetics and pharmacodynamics (PK/PD) of irbesartan in Beagle dogs after oral administration at two dose rates

Irbesartan (Irb) is an angiotensin II type 1 receptor antagonist widely used in humans to treat hypertension. Age-related diseases such as hypertension are increasingly being diagnosed in dogs and there is the need for new drugs. The PK/PD of Irb was tested in Beagle dogs. Ten healthy Beagles were orally administered two dose rates (2 and 5 mg/kg), according to a cross over study design. Blood collections for PK analysis and systolic blood pressure (SBP), heart and respiratory rate, mucous membranes colour, capillary refill time and temperature evaluations were performed at scheduled intervals. The drug plasma concentration was dose dependent. The dogs administered 5 mg/kg showed a significant reduction in SBP, while in those receiving 2 mg/kg, this parameter was minimally affected. A counter clockwise hysteresis showed no direct correlation between SBP and plasma concentrations. The minimum effective concentration was theorized to be within the range 550-800 ng/mL. Although further studies are necessary, 5 mg/kg seems to be the more appropriate dose to obtain a hypotensive effect in Beagle dogs.